FIG. 1A is a cross section of an existing clamping device for an information recording disk indicating the condition before clamping. FIG. 1B is a cross section indicating the condition after clamping. In both FIG. 1A and FIG. 1B, a magnet clamper 1 (hereinafter referred to as clamper) has a collar 1a that is inserted in a hole 2a of a plate 2 and is movable in the direction of the arrow A1.
A tapered wheel 3 is arranged to oppose the clamper 1. The tapered wheel 3 is mounted to a spindle shaft 4.
The spindle shaft 4 is provided with a support wheel 5. A disk 6 is supported by the support wheel 5.
Before the unclamped condition shown in FIG. 1A changes to the clamped condition shown in FIG. 1B, the clamper 1 is supported by, and suspended from, the plate 2 that engages the collar 1a. When the plate 2 moves downward to the disk clamping condition, the clamper 1 also moves until the disk 6 is held by the clamper 1 and the support wheel 5. Moreover, the plate 2 moves downward to the condition shown in FIG. 1B. As a result, the plate 2 is separated from the rotating part and the disk 6 can be freely rotated.
To release the disk from the clamped position, the plate 2 moves upward, hooking the flange 1a at the upper part of the clamper 1 until the condition shown in FIG. 1A is regained.
In an attempt to prevent vibration when a disk is to be used in a car stereo, a mechanism part, including the spindle 4 is often floated from another mechanism by an insulator, etc. In this case, in the condition shown in FIG. 1B, when the vibration amplitude is large, the clamper 1 may collide with the plate 2 to cause a situation where there is no clearance 2b between the rotating part including the clamper 1 and the hole 2a.
To avoid this, a large clearance is required and in such a case, the clamper 1 must move a long distance in the hole 2a of the plate 2 to return to the condition shown in FIG. 1A. During the movement, the center of the clamper 1 can deviate from the position of the spindle shaft 4 to disable clamping.